Solvent Effects on the Spin-Transition in a Series of Fe(II) Dinuclear Triple Helicate Compounds

This work explores the effect of lattice solvent on the observed solid-state spin-transition of a previously reported dinuclear Fe(II) triple helicate series 1–3 of the general form [FeII2L3](BF4)4(CH3CN)n, where L is the Schiff base condensation product of imidazole-4-carbaldehyde with 4,4-diaminodiphenylmethane (L1), 4,4′-diaminodiphenyl sulfide (L2) and 4,4′-diaminodiphenyl ether (L3) respectively, and 1 is the complex when L = L1, 2 when L = L2 and 3 when L = L3 (Craze, A.R.; Sciortino, N.F.; Bhadbhade, M.M.; Kepert, C.J.; Marjo, C.E.; Li, F. Investigation of the Spin Crossover Properties of Three Dinuclear Fe(II) Triple Helicates by Variation of the Steric Nature of the Ligand Type. Inorganics. 2017, 5 (4), 62). Desolvation of 1 and 2 during measurement resulted not only in a decrease in T1/2 and completeness of spin-crossover (SCO) but also a change in the number of steps in the spin-profile. Compounds 1 and 2 were observed to change from a two-step 70% complete transition when fully solvated, to a single-step half complete transition upon desolvation. The average T1/2 value of the two-steps in the solvated materials was equivalent to the single T1/2 of the desolvated sample. Upon solvent loss, the magnetic profile of 3 experienced a transformation from a gradual SCO or weak antiferromagnetic interaction to a single half-complete spin-transition. Variable temperature single-crystal structures are presented and the effects of solvent molecules are also explored crystallographically and via a Hirshfeld surface analysis. The spin-transition profiles of 1–3 may provide further insight into previous discrepancies in dinuclear triple helicate SCO research reported by the laboratories of Hannon and Gütlich on analogous systems (Tuna, F.; Lees, M. R.; Clarkson, G. J.; Hannon, M. J. Readily Prepared Metallo-Supramolecular Triple Helicates Designed to Exhibit Spin-Crossover Behaviour. Chem. Eur. J. 2004, 10, 5737–5750 and Garcia, Y.; Grunert, C. M.; Reiman, S.; van Campenhoudt, O.; Gütlich, P. The Two-Step Spin Conversion in a Supramolecular Triple Helicate Dinuclear Iron(II) Complex Studied by Mössbauer Spectroscopy. Eur. J. Inorg. Chem. 2006, 3333–3339).

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Spin-Crossover 2-D Hofmann Frameworks Incorporating an Amide-Functionalized Ligand: N-(pyridin-4-yl)benzamide

Chemistry ◽

10.3390/chemistry3010026 ◽

2021 ◽

Vol 3 (1) ◽

pp. 360-372

Author(s):

Xandria Ong ◽

Manan Ahmed ◽

Luonan Xu ◽

Ashley T. Brennan ◽

Carol Hua ◽

...

Keyword(s):

Hydrogen Bonding ◽

Spin State ◽

Spin Crossover ◽

Variable Temperature ◽

Spin Transition ◽

Single Step ◽

Amide Group ◽

State Transitions ◽

Structure Property ◽

Scanning Calorimetry

Two analogous 2-D Hofmann-type frameworks, which incorporate the novel ligand N-(pyridin-4-yl)benzamide (benpy) [FeII(benpy)2M(CN)4]·2H2O (M = Pd (Pd(benpy)) and Pt (Pt(benpy))) are reported. The benpy ligand was explored to facilitate spin-crossover (SCO) cooperativity via amide group hydrogen bonding. Structural analyses of the 2-D Hofmann frameworks revealed benpy-guest hydrogen bonding and benpy-benpy aromatic contacts. Both analogues exhibited single-step hysteretic spin-crossover (SCO) transitions, with the metal-cyanide linker (M = Pd or Pt) impacting the SCO spin-state transition temperature and hysteresis loop width (Pd(benpy): T½↓↑: 201, 218 K, ∆T: 17 K and Pt(benpy): T½↓↑: 206, 226 K, ∆T: 20 K). The parallel structural and SCO changes over the high-spin to low-spin transition were investigated using variable-temperature, single-crystal, and powder X-ray diffraction, Raman spectroscopy, and differential scanning calorimetry. These studies indicated that the ligand–guest interactions facilitated by the amide group acted to support the cooperative spin-state transitions displayed by these two Hofmann-type frameworks, providing further insight into cooperativity and structure–property relationships.

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Varied spin crossover behaviour in a family of dinuclear Fe(ii) triple helicate complexes

Dalton Transactions ◽

10.1039/c8dt01567h ◽

2018 ◽

Vol 47 (24) ◽

pp. 7965-7974 ◽

Cited By ~ 8

Author(s):

Rosanna J. Archer ◽

Hayley S. Scott ◽

Matthew I. J. Polson ◽

Bryce E. Williamson ◽

Corine Mathonière ◽

...

Keyword(s):

Spin Crossover ◽

Variable Temperature ◽

Triple Helicate

A family of dinuclear Fe(ii) triple helicate complexes has been structurally characterised and their spin crossover behaviour studied using a variety of variable temperature physical techniques.

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Solution-State Spin Crossover in a Family of [Fe(L)2(CH3CN)2](BF4)2 Complexes

Magnetochemistry ◽

10.3390/magnetochemistry5020022 ◽

2019 ◽

Vol 5 (2) ◽

pp. 22

Author(s):

Benjamin Wilson ◽

Hayley Scott ◽

Rosanna Archer ◽

Corine Mathonière ◽

Rodolphe Clérac ◽

...

Keyword(s):

Thermodynamic Parameters ◽

General Formula ◽

Spin Crossover ◽

Variable Temperature ◽

Spectroscopic Studies ◽

Solution State ◽

Uv Visible ◽

State Spin

We report herein on five new Fe(II) complexes of general formula [Fe(L)2(NCCH3)2](BF4)2•xCH3CN (L = substituted 2-pyridylimine-based ligands). The influence of proximally located electron withdrawing groups (e.g., NO2, CN, CF3, Cl, Br) bound to coordinated pyridylimine ligands has been studied for the effect on spin crossover in their Fe(II) complexes. Variable-temperature UV-visible spectroscopic studies performed on complexes with more strongly electronegative ligand substituents revealed spin crossover (SCO) in the solution, and thermodynamic parameters associated with the spin crossover were estimated.

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A large dinuclear Fe(ii) triple helicate demonstrating a two-step spin crossover

Chemical Communications ◽

10.1039/d0cc03708g ◽

2020 ◽

Vol 56 (62) ◽

pp. 8838-8841

Author(s):

Kyle J. Howard-Smith ◽

Alexander R. Craze ◽

Hikaru Zenno ◽

Junya Yagyu ◽

Shinya Hayami ◽

...

Keyword(s):

Spin Crossover ◽

Spin Transition ◽

Triple Helicate

The largest reported dinuclear Fe(ii) triple helicate system to exhibit spin crossover is presented, with exploration of the two-step spin-transition.

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Variable temperature far and mid FT-IR as a valuable tool to determine the spin transition temperature of iron(II) spin-crossover coordination compounds

Vibrational Spectroscopy ◽

10.1016/j.vibspec.2003.07.006 ◽

2004 ◽

Vol 34 (1) ◽

pp. 175-186 ◽

Cited By ~ 21

Author(s):

Peter Weinberger ◽

Matthias Grunert

Keyword(s):

Transition Temperature ◽

Coordination Compounds ◽

Spin Crossover ◽

Variable Temperature ◽

Spin Transition ◽

Ft Ir

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The Number and Shape of Lattice Solvent Molecules Controls Spin-Crossover in an Isomorphous Series of Crystalline Solvate Salts

Chemical Communications ◽

10.1039/d1cc02624k ◽

2021 ◽

Author(s):

Izar Capel Berdiell ◽

Rafal Kulmaczewski ◽

Namrah Shahid ◽

Oscar Cespedes ◽

Malcolm Halcrow

Keyword(s):

Spin Crossover ◽

Spin Transition ◽

Solvent Molecules ◽

Crystalline Solvate

Crystals of [FeL2][BF4]2·nMeCN (L = N-(2,6-di{pyrazol-1-yl}pyrid-4-yl)acetamide; n = 1 or 2) and [FeL2][ClO4]2·MeCN are isomorphous. When n = 1 the compounds exhibit an abrupt, hysteretic spin-transition below 200 K, but...

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Structural studies of a flexible 2D layer spin crossover coordination polymer

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273314087610 ◽

2014 ◽

Vol 70 (a1) ◽

pp. C1238-C1238

Author(s):

Yu-Chun Chuang ◽

Chung-Kai Chang ◽

Ching-Che Kao ◽

Jey-Jau Lee ◽

Chih-Chieh Wang

Keyword(s):

Magnetic Property ◽

Spin State ◽

Spin Crossover ◽

Layer Structure ◽

Dominant Role ◽

Spin Transition ◽

High Spin State ◽

Structural Studies ◽

Synchrotron Powder Diffraction ◽

Solvent Molecules

The first coordination sphere of spin crossover material has been comprehended to play a dominant role to its magnetic property. However, the intermolecular interactions, such as π···π interaction and hydrogen bonding, also play a crucial factor. The contents of the solvent in a 2D layer structure, Fe (μ-atrz)(μ-pyz)(NCS)2·nH2O where n=4, 2 and 0, has been reported to be able to affect the spin transition behavior dramatically.[1] As loss of solvent molecules, the inter-layer distance becomes shorter and the transition temperature shifts to lower temperature and accompanies a larger hysteresis loop. To further understand the correlation between the inter-layer distance and magnetic property, the guest ab/desorption and pressure-induced synchrotron powder diffraction experiments were performed at BL01C2 in NSRRC. Based on the cyclic TGA measurements, the guest molecules, H2O, MeOH and EtOH, all can be removed and retaken repeatedly. The pressure-induced PXRD experiment was performed using a Boehler-Almax design diamond anvil cell (DAC). The detail structural studies attempt to understand not only the spin state changes from HS (high spin state) to LS (low spin state) but also the cooperative effect through the inter-layer distance.

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2D Layer Arrangement of Solely [HS-HS] or [LS-LS] Molecules in the [HS-LS] State of a Dinuclear Fe(II) Spin Crossover Complex

Crystals ◽

10.3390/cryst10060448 ◽

2020 ◽

Vol 10 (6) ◽

pp. 448

Author(s):

Fabian Fürmeyer ◽

Luca M. Carrella ◽

Eva Rentschler

Keyword(s):

Crystal Structure ◽

Spin Crossover ◽

Crystal Packing ◽

Spin Transition ◽

High Spin State ◽

Crystal Structure Analysis ◽

Magnetic Data ◽

The Novel ◽

Layer Arrangement ◽

Dinuclear Iron

Herein we report the synthesis and characterization of three new dinuclear iron(II) complexes [FeII2(I4MTD)2](F3CSO3)4 (C1), [FeII2(I4MTD)2](ClO4)4 (C2) and [FeII2(I4MTD)2](BF4)4 (C3) based on the novel ligand (I4MTD = 2,5-bis{[(1H-imidazol-4-ylmethyl)amino]methyl}-1,3,4-thiadiazole). Magnetic susceptibility measurements and single-crystal structure analysis show that the iron(II) spin centers for all complexes are in the high spin state at high temperatures. While the magnetic data of air-dried samples confirm the [HS-HS] state for C1 and C2 down to very low temperature, for C3, a gradual spin crossover is observed below 150 K. The crystal structure of C3·THF at 100 K shows that a spin transition from [HS-HS] to an intermediate state takes place, which is a 1:1 mixture of discrete [HS-HS] and [LS-LS] molecules, as identified unambiguously by crystallography. The different SCO properties of C1–C3 can be attributed to crystal packing effects in the solid state.

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Hysteretic Thermal Spin-Crossover and Symmetry Breaking in Heteroleptic Fe(II) Complexes Using Alkyl Chain Substituted 2,2’-Dipyridylamine Ligands

10.26434/chemrxiv.9641990 ◽

2019 ◽

Author(s):

Blaise Geoghegan ◽

Wasinee Phonsri ◽

Peter Horton ◽

James Orton ◽

Simon Coles ◽

...

Keyword(s):

Phase Transition ◽

Spin Crossover ◽

Alkyl Chain ◽

Thermal Hysteresis ◽

Variable Temperature ◽

Spin Transition ◽

Magnetic Data ◽

Monoclinic Space Group ◽

Space Group ◽

Bond Lengths

The alkyl chain carrying ligands N,N-di(pyridin-2-yl)butanamide (LC4) and N,N-di(pyridin-2-yl)decanamide (LC10) were combined with NCS- co-ligands to form the neutral heteroleptic Fe(II) complexes trans-[FeII(LC4)2(NCS)2] (1C4) and trans [FeII(LC10)2(NCS)2] (1C10). Variable temperature crystallographic studies revealed that 1C4 is in the orthorhombic space group Pna21 between 85-200 K whereas 1C10 is in the monoclinic space group P21/c between 85-105 K before undergoing a crystallographic phase transition to the triclinic space group P1􀴤 by 140 K. The average Fe-N bond lengths suggest that at 85 K 1C4 contains LS Fe(II) centres; However, the ca. 0.18 Å increase in the average Fe-N bond lengths between 85 and 120 K suggests a spin-transition occurs within this temperature interval and the HS state is predominant beyond this. 1C10 contains LS Fe(II) centres between 85 and 105 K. Upon warming from 105 to 140 K the average Fe-N bond lengths increase by ca. 0.19 Å, which suggests that a spin-transition to the HS accompanies the P21/c to P1􀴤 crystallographic phase transition. Solid-state magnetic susceptibility measurements showed that 1C4 undergoes semi-abrupt spin-crossover with T1/2 = 127.5 K and a thermal hysteresis of ca. 13 K whereas, 1C10 undergoes an abrupt spin-crossover with T1/2 = 119.0 K, and is also accompanied by thermal hysteresis of ca. 4 K. The crystallographic and magnetic data show that the length of the complex’s alkyl chain substituents can have a large impact on the structure of the crystal lattice as well as a subtle effect on the T1/2 value for thermal spin-crossover.

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